Shell and tube type heat exchangers are a common type in use today, particularly in nuclear power plants. One type used passes a heating fluid, such as high temperature water or vapor, through the tubes, which gives up heat to water which flows outside of the tubes, thus generating steam.
Vapor generators of this type commonly employ tube bundles formed of layers of U-shaped tubes, the ends of whose legs are secured to a tubesheet disposed at one end of the shell while the tube bends are located at the opposite end of the shell. Because these tubes have legs of considerable length, especially in high capacity generators, they are susceptible to flow and/or mechanically induced vibrations, and tube spacer and support members are used in the bend area of the tubes. These spacer and support members must be thin enough so that they do not substantially restrict flow of the heated fluid, while still being rigid enough to perform their intended function. In some units which have been in operation for long periods of time, problems have developed, in that the ends of the support plates which extend beyond the boundaries of the tube bundle have vibrated to such an extent that their continued contact with or banging against the tubes in the first two or three rows of the tube bundle have caused wear or damage to these tubes. Thus the problem presently faced is how to prevent the support plates from causing further damage to the tubes, while continuing to adequately space and support these tubes.